Recently, there is a general demand for cast products of higher quality. In this perspective, there is provided in JP Patent Kokai JP-A-7-256422 a casting device for a metal product. This casting device includes a metal die unit, having a pressurizing chamber for holding a metal material of, for example, an aluminum alloy in the solid-liquid co-existing state, and a casting cavity into which the metal material flows to form a cast product, a pressurizing cylinder for pressurizing the metal material held in the pressurizing chamber of the metal die unit to cause the pressurized material to flow into the casting cavity to produce a cast product, and a stripping blade abutting against the outer layer of the metal material and pressurized by a pressurizing plunger, to strip off the outer layer.
The outer layer of the metal material is exposed to air and hence is liable to be contaminated by impurities such as oxides. Additionally, the outer layer of the metal material is quenched by the inner wall surface of a chamber for molten metal material and hence is likely to be of a transmuted texture. Moreover, if a die coating agent for lubrication or thermal resistance is applied to the inner wall surface of the pressurizing chamber, the die coating agent tends to become affixed to the outer layer of the metal material. Impurities, transmuted structure or the die coating agent, if allowed to flow into the casting cavity, are deleterious to the quality of the cast product. Thus, with the above-identified casting device for a metal product, when the metal material is pressurized by the pressurizing cylinder so as to flow into the casting cavity, the outer layer of the metal material is scraped with a scraping edge, such as a blade. This prohibits the impurities, transmuted structure or the die coating agent from being entrained into the cast product to achieve an improved quality of the cast product.
Meanwhile, there is much to be desired in the art for further improvement. In the above-described casting device for a metal product, the scraper edge of the blade unit nips into the metal material. The result is that, when the operation of scraping off the outer layer of the metal material has come to a close, it is not so easy to separate the blade unit from the metal material.
Thus, in the above-identified publication, a second blade unit is provided on the pressurizing plunger, in addition to the blade unit provided within the metal die unit. When the scraping operation for the outer layer of the metal material comes to a close, the metal material is punched and severed under the shearing force generated by the blade unit within the metal die unit and the second blade unit of the pressuring plunger, thereby completely separating the metal material and the blade unit. In such case, the second blade unit must be provided to the pressurizing plunger, thus possibly raising the equipment cost.
In view of the above-depicted states of the art, there is much to be desired in the art for further improvement.